Now we turn to the latest on the 19-year-old terror suspect held in solitary confinement in boston. We have learned that the fbi is casting a wider net. Abc's chief investigative correspondent brian ross with the latest. Reporter: It was only a few months ago that dzhokhar tsarnaev posted this video of himself online playfully teasing his brother's daughter. Today the 19-year-d is at the devens federal medical center outside boston. Confined by himself it a tiny cell, a taste of what awaits him if convicted of the marathon bombing. He doesn't have a life, period. His total existence will be lockdown. Reporter: Meantime, fbi agents are widening their net in looking for possible accomplices of the two brothers in the bombing. Some may have been involved upon haddinghe bombs, others may have helped radicalize the brothers. Reporter: Fbi agents today also continued to press the widow of the elder tsarnaev brother, katherine russell, about her knowledge of her husband's activities. Agents left her house carrying evidence bags, and she was seen leaving with her attorneys, who have said she did not know about the bomb plot. And the investigative threads continue to stretch into russia. At the same time the elder tamerlan traveled there last year, two key young leaders of a violent islamist group were killed by russian forces. One of them was a canadian, william plotnikov, who, like tamerlan, had been a professional boxer before evolving into a radical jihadist. Tamerlan left russia two days after the canadian was killed and the fbi wants to know if he helped recruit and train tamerlan. While he was there. If you want to learn how to build a bomb, chechnya is a good place to do it. As the net widens, people briefed on the case say the fbi has almost a dozen individuals, both in russia, and here in the u.S., Who it currently considers persons of interest. Late today, officials told pierre thomas at abc news, that investigators had discovered female dna on fragments of one of the bombs, but that it's unclear whether it's from a victim or someone who handled the parts innocently or as a possible co-conspirator. Thanks, brian. We move on now, six months

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